US20200005823A1 - Heat-assisted magnetic recording medium and magnetic storage apparatus - Google Patents
Heat-assisted magnetic recording medium and magnetic storage apparatus Download PDFInfo
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- US20200005823A1 US20200005823A1 US16/448,187 US201916448187A US2020005823A1 US 20200005823 A1 US20200005823 A1 US 20200005823A1 US 201916448187 A US201916448187 A US 201916448187A US 2020005823 A1 US2020005823 A1 US 2020005823A1
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- 230000005291 magnetic effect Effects 0.000 title claims abstract description 165
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims abstract description 61
- 239000000395 magnesium oxide Substances 0.000 claims abstract description 41
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 claims abstract description 39
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 claims abstract description 21
- 239000011787 zinc oxide Substances 0.000 claims abstract description 21
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 16
- 239000000956 alloy Substances 0.000 claims abstract description 16
- 150000001875 compounds Chemical class 0.000 claims abstract description 14
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 claims abstract description 12
- 239000000758 substrate Substances 0.000 claims abstract description 11
- INZDTEICWPZYJM-UHFFFAOYSA-N 1-(chloromethyl)-4-[4-(chloromethyl)phenyl]benzene Chemical compound C1=CC(CCl)=CC=C1C1=CC=C(CCl)C=C1 INZDTEICWPZYJM-UHFFFAOYSA-N 0.000 claims abstract description 10
- SKKMWRVAJNPLFY-UHFFFAOYSA-N azanylidynevanadium Chemical compound [V]#N SKKMWRVAJNPLFY-UHFFFAOYSA-N 0.000 claims abstract description 9
- XHCLAFWTIXFWPH-UHFFFAOYSA-N [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] XHCLAFWTIXFWPH-UHFFFAOYSA-N 0.000 claims abstract description 4
- 229910001887 tin oxide Inorganic materials 0.000 claims abstract description 4
- 229910001935 vanadium oxide Inorganic materials 0.000 claims abstract description 4
- 239000000126 substance Substances 0.000 claims description 10
- 239000010410 layer Substances 0.000 description 57
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 14
- 230000000052 comparative effect Effects 0.000 description 14
- 239000011651 chromium Substances 0.000 description 11
- 239000013078 crystal Substances 0.000 description 10
- 238000000034 method Methods 0.000 description 8
- 239000000463 material Substances 0.000 description 7
- 239000011241 protective layer Substances 0.000 description 7
- 239000000377 silicon dioxide Substances 0.000 description 7
- AMWRITDGCCNYAT-UHFFFAOYSA-L hydroxy(oxo)manganese;manganese Chemical compound [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 description 6
- 230000008878 coupling Effects 0.000 description 5
- 238000010168 coupling process Methods 0.000 description 5
- 238000005859 coupling reaction Methods 0.000 description 5
- 238000005259 measurement Methods 0.000 description 5
- 229910005335 FePt Inorganic materials 0.000 description 4
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 4
- 229910021541 Vanadium(III) oxide Inorganic materials 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 229910052697 platinum Inorganic materials 0.000 description 4
- 238000005204 segregation Methods 0.000 description 4
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 3
- 229910000420 cerium oxide Inorganic materials 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- KELHQGOVULCJSG-UHFFFAOYSA-N n,n-dimethyl-1-(5-methylfuran-2-yl)ethane-1,2-diamine Chemical compound CN(C)C(CN)C1=CC=C(C)O1 KELHQGOVULCJSG-UHFFFAOYSA-N 0.000 description 3
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 3
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 3
- SIWVEOZUMHYXCS-UHFFFAOYSA-N oxo(oxoyttriooxy)yttrium Chemical compound O=[Y]O[Y]=O SIWVEOZUMHYXCS-UHFFFAOYSA-N 0.000 description 3
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 3
- 229910001928 zirconium oxide Inorganic materials 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 229910018979 CoPt Inorganic materials 0.000 description 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 238000007737 ion beam deposition Methods 0.000 description 2
- 239000000314 lubricant Substances 0.000 description 2
- 229910001004 magnetic alloy Inorganic materials 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- BPUBBGLMJRNUCC-UHFFFAOYSA-N oxygen(2-);tantalum(5+) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ta+5].[Ta+5] BPUBBGLMJRNUCC-UHFFFAOYSA-N 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- 229910052718 tin Inorganic materials 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 239000010936 titanium Substances 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- GPPXJZIENCGNKB-UHFFFAOYSA-N vanadium Chemical compound [V]#[V] GPPXJZIENCGNKB-UHFFFAOYSA-N 0.000 description 2
- 229910052725 zinc Inorganic materials 0.000 description 2
- 239000011701 zinc Substances 0.000 description 2
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 229910019582 Cr V Inorganic materials 0.000 description 1
- 229910000914 Mn alloy Inorganic materials 0.000 description 1
- 229910001182 Mo alloy Inorganic materials 0.000 description 1
- 229910003310 Ni-Al Inorganic materials 0.000 description 1
- 229910000929 Ru alloy Inorganic materials 0.000 description 1
- 229910001069 Ti alloy Inorganic materials 0.000 description 1
- NRTOMJZYCJJWKI-UHFFFAOYSA-N Titanium nitride Chemical compound [Ti]#N NRTOMJZYCJJWKI-UHFFFAOYSA-N 0.000 description 1
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 description 1
- 229910001080 W alloy Inorganic materials 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 229910000423 chromium oxide Inorganic materials 0.000 description 1
- QDOXWKRWXJOMAK-UHFFFAOYSA-N dichromium trioxide Chemical compound O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 230000005389 magnetism Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 239000010702 perfluoropolyether Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 229910001936 tantalum oxide Inorganic materials 0.000 description 1
- 239000004408 titanium dioxide Substances 0.000 description 1
Images
Classifications
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
- G11B5/4806—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed specially adapted for disk drive assemblies, e.g. assembly prior to operation, hard or flexible disk drives
- G11B5/4866—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed specially adapted for disk drive assemblies, e.g. assembly prior to operation, hard or flexible disk drives the arm comprising an optical waveguide, e.g. for thermally-assisted recording
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/62—Record carriers characterised by the selection of the material
- G11B5/64—Record carriers characterised by the selection of the material comprising only the magnetic material without bonding agent
- G11B5/66—Record carriers characterised by the selection of the material comprising only the magnetic material without bonding agent the record carriers consisting of several layers
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/62—Record carriers characterised by the selection of the material
- G11B5/73—Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer
- G11B5/7368—Non-polymeric layer under the lowermost magnetic recording layer
- G11B5/7369—Two or more non-magnetic underlayers, e.g. seed layers or barrier layers
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/62—Record carriers characterised by the selection of the material
- G11B5/73—Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer
- G11B5/7368—Non-polymeric layer under the lowermost magnetic recording layer
- G11B5/7375—Non-polymeric layer under the lowermost magnetic recording layer for heat-assisted or thermally-assisted magnetic recording [HAMR, TAMR]
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/74—Record carriers characterised by the form, e.g. sheet shaped to wrap around a drum
- G11B5/82—Disk carriers
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B2005/0002—Special dispositions or recording techniques
- G11B2005/0005—Arrangements, methods or circuits
- G11B2005/0021—Thermally assisted recording using an auxiliary energy source for heating the recording layer locally to assist the magnetization reversal
Definitions
- the disclosures herein generally relate to a heat-assisted magnetic recording medium and a magnetic storage apparatus.
- a heat-assisted recording method by which a surface is locally heated by irradiating a magnetic recording medium with near-field light or the like such that writing on the magnetic recording medium is performed by reducing the magnetic coercivity of the magnetic recording medium, is known as a next-generation recording method that can realize an areal recording density of approximately 1 Tbit/inch 2 .
- a heat-assisted recording method it is possible to easily write on a magnetic recording medium having a coercivity of several tens of kOe at ambient temperature by the recording magnetic field of a magnetic head. Therefore, a high Ku material whose crystal magnetic anisotropic constant Ku is on the order of 10 6 J/m 3 can be used for a magnetic layer.
- the grain size of magnetic grains can be reduced to 6 nm or less.
- alloys such as FePt alloys (Ku ⁇ 7 ⁇ 10 6 J/m 3 ) having an L1 0 structure and CoPt alloys (Ku ⁇ 5 ⁇ 10 6 J/m 3 ) are known.
- the magnetic layer is required to be (001) oriented in order to enhance the crystal orientation of the magnetic layer. For this reason, for an underlayer, it is preferable to use (100) oriented MgO.
- the (100) plane of MgO lattice-matches the (001) plane of a FePt alloy having an L1 0 structure.
- an underlayer is formed that includes MgO as a main component and includes at least one kinds of oxide selected from SiO 2 , TiO 2 , Cr 2 O 3 , Al 2 O 3 , Ta 2 O 5 , ZrO 2 , Y 2 O 3 , CeO 2 , MnO, TiO, and ZnO (for example, see Patent Document 1).
- Patent Document 1 Japanese Laid-Open Patent Publication No. 2011-165232
- a heat-assisted magnetic recording medium includes: a substrate; an underlayer; and a magnetic layer including an alloy having an L1 0 structure.
- the substrate, the underlayer, and the magnetic layer are stacked in the recited order.
- the underlayer includes a first underlayer.
- the first underlayer includes magnesium oxide and one or more compounds selected from the group consisting of vanadium oxide, zinc oxide, tin oxide, vanadium nitride, and vanadium carbide, and a total content of the one or more compounds is in a range of 45 mol % to 70 mol %.
- a magnetic storage apparatus includes: the heat-assisted magnetic recording medium according to (1).
- FIG. 1 is a cross-sectional view illustrating an example of a layer structure of a heat-assisted magnetic recording medium according to an embodiment
- FIG. 2 is a cross-sectional view illustrating another example of a layer structure of a heat-assisted magnetic recording medium according to the embodiment
- FIG. 3 is a perspective view illustrating an example of a magnetic storage apparatus according to the embodiment.
- FIG. 4 is a schematic diagram illustrating an example of a magnetic head used in the magnetic storage apparatus of FIG. 3 .
- FIG. 1 is a schematic diagram illustrating an example of a layer structure of a heat-assisted magnetic recording medium 100 A according to an embodiment.
- the heat-assisted magnetic recording medium 100 A includes a substrate 1 , an underlayer 2 A, and a magnetic layer 3 including an alloy having an L1 0 structure in this order.
- a second underlayer 4 and a first underlayer 5 are stacked in this order.
- the first underlayer 5 includes magnesium oxide and one or more compounds selected from the group consisting of vanadium oxide, zinc oxide, tin oxide, vanadium nitride, and vanadium carbide. The total content of the above described one or more compounds is in a range of 45 mol % to mol %.
- the second underlayer 4 includes magnesium oxide.
- the (001) orientation of the magnetic layer 3 including an alloy having an L1 0 structure is enhanced.
- the magnetic grains contained in the magnetic layer 3 are made finer and exchange coupling between the magnetic grains is reduced. As a result, the coercivity of the heat-assisted magnetic recording medium 100 A is enhanced.
- the second underlayer 4 comprising magnesium oxide is (100)-oriented
- the first underlayer 5 including magnesium oxide having a NaCl type structure is (100)-oriented.
- the (100) plane of the first underlayer 5 lattice-matches the (001) plane of the magnetic layer 3 having an L1 0 type crystal structure, and the (001) orientation of the magnetic layer 3 is enhanced.
- Magnesium oxide grains contained in the first underlayer 5 are made finer by the above-described one or more compounds, which are contained in the first underlayer 5 . Then, “One by one growth” is promoted in which one magnetic crystal grain constituting the magnetic layer 3 grows on one magnesium oxide crystal grain. As a result, the (001) orientation of the magnetic layer 3 is enhanced. Also, the magnetic grains contained in the magnetic layer 3 can be made finer, separation between the magnetic grains can be prompted, and exchange coupling between the magnetic grains can be reduced.
- the first underlayer 5 is in contact with the magnetic layer 3 , but the first underlayer 5 may not be in contact with the magnetic layer 3 .
- vanadium, zinc, or tin in the metal state when being in contact with magnetic grains, at least portion of vanadium, zinc, or tin in the metal state diffuses into the magnetic grains and the magnetism of the magnetic grains decreases.
- the content of the above-described one or more compounds in the first underlayer 5 is in a range of 45 mol % to 70 mol %, and is preferably in a range of 45 mol % to 55 mol %. If the content of the above-described one or more compounds in the first underlayer 5 is less than 45 mol %, the magnesium oxide grains in the first underlayer 5 cannot be sufficiently made finer. If the content of the above-described one or more compounds exceeds 70 mol %, the variance of the grain diameters of the magnesium oxide grains included in the first underlayer 5 increases and the (100) orientation of the first underlayer 5 decreases.
- the content of magnesium oxide in the first underlayer 5 is preferably greater than or equal to 30 mol %, and is more preferably greater than or equal to 45 mol %.
- the (100) orientation of the first underlayer 5 is enhanced when the content of magnesium oxide in the first underlayer 5 is greater than or equal to 30 mol %.
- the thickness of the first underlayer 5 is preferably in a range of 0.2 nm to 2 nm, and is more preferably in a range of 0.5 nm to 1.5 nm.
- the thickness of the first underlayer 5 is 0.2 nm or more, magnesium oxide grains contained in the first underlayer 5 can be further miniaturized, and when the thickness of the first underlayer 5 is 2 nm or less, the heat dissipation property when writing information to the heat-assisted magnetic recording medium 100 A can be further enhanced.
- the content of magnesium oxide in the second underlayer 4 is preferably greater than or equal to 50 mol %, and is more preferably greater than or equal to 70 mol %. When the content of magnesium oxide in the second underlayer 4 is 50 mol % or more, the (100) orientation of the second underlayer 4 is enhanced.
- An alloy having an L1 0 structure contained in the magnetic layer 3 is preferably a FePt magnetic alloy or a CoPt magnetic alloy.
- the magnetic layer 3 preferably includes a grain boundary segregation material for magnetic grains.
- the magnetic layer 3 has a granular structure in which the magnetic grains having an L1 0 structure are divided by the grain boundary segregation material.
- an oxide such as silicon dioxide (SiO 2 ), titanium dioxide (TiO 2 ), chromium oxide (Cr 2 O 3 ), aluminum oxide (Al 2 O 3 ), tantalum oxide (Ta 2 O 5 ), zirconium oxide (ZrO 2 ), yttrium oxide (Y 2 O 3 ), cerium oxide (CeO 2 ), manganese oxide (MnO), titanium monoxide (TiO), or zinc oxide (ZnO), carbon (C), a carbide such as vanadium carbide (VC), a nitride such as vanadium nitride (VN), boron nitride (BN), titanium nitride (TiN), or the like may be used. Two or more of these may be used in combination as the grain boundary segregation material for magnetic grains.
- a protective layer is formed on the magnetic layer 3 in the heat-assisted magnetic recording medium 100 A.
- a method of forming the protective layer is not limited to a particular method.
- a RF-CVD (Radio Frequency-Chemical Vapor Deposition) method that decomposes a source gas made of hydrocarbon by high-frequency plasma
- an IBD (Ion Beam Deposition) method that ionizes a source gas by electrons emitted from a filament
- a FCVA (Filtered Cathodic Vacuum Arc) method that uses a solid carbon target without using a source gas, or the like may be used to form the protective layer.
- the thickness of the protective layer is preferably 1 nm or more and 6 nm or less.
- the floating properties of the magnetic head become satisfactory when the thickness of the protective layer is 1 nm or more.
- a magnetic spacing decreases and the SNR of the heat-assisted magnetic recording medium 100 A is enhanced when the thickness of the protective layer is 6 nm or less.
- a lubricant layer including a perfluoropolyether-based lubricant may be further formed on the protective layer.
- FIG. 2 illustrates another example of a layer configuration of a heat-assisted magnetic recording medium 100 B according to the present embodiment.
- the heat-assisted magnetic recording medium 100 B has a configuration similar to that of the heat-assisted magnetic recording medium 100 A with the exception that an underlayer 2 B is formed instead of the underlayer 2 A.
- heat-assisted magnetic recording medium 100 B elements that are the same as those of the heat-assisted magnetic recording medium 100 A are referred to by the same reference numerals, and duplicate descriptions may be omitted as appropriate.
- the underlayer 2 B has a configuration the same as that of the underlayer 2 A with the exception that a second underlayer 4 is not formed and a second underlayer 6 is formed between the first underlayer 5 and the magnetic layer 3 .
- the second underlayer 6 includes a substance having a BCC structure or a B2 structure.
- the second underlayer 6 including the substance having the BCC structure or the B2 structure is (100)-oriented.
- the (100) plane of the second underlayer 6 lattice-matches the (001) plane of the magnetic layer 3 having an L1 0 structure, and the (001) orientation of the magnetic layer 3 is enhanced.
- Magnesium oxide grains contained in the first underlayer 5 are made finer by the above-described one or more compounds, which are contained in the first underlayer 5 . Then, “One by one growth” is promoted in which one crystal grain of the substance having the BCC structure or the B2 structure constituting the second underlayer 6 heteroepitaxially grows on one magnesium oxide crystal grain. Also, “One by one growth” is promoted in which one magnetic crystal grain constituting the magnetic layer 3 grows on one crystal grain of the substance having the BCC structure or the B2 structure. As a result, the (001) orientation of the magnetic layer 3 is enhanced. Also, the magnetic grains contained in the magnetic layer 3 can be made finer, separation between the magnetic grains can be prompted, and exchange coupling between the magnetic grains can be reduced.
- Examples of the substance having the BCC structure included in the second underlayer 6 include Cr, a Cr—Mn alloy, a Cr—Mo alloy, a Cr—W alloy, a Cr—V alloy, a Cr—Ti alloy, a Cr—Ru alloy, and the like.
- Examples of the substance having the B2 structure included in the second underlayer 6 include a Ru—Al alloy, a Ni—Al alloy, and the like.
- the content of the substance having the BCC or B2 structure in the second underlayer 6 is preferably greater than or equal to 60 mol %, and is more preferably greater than or equal to 80 mol %.
- the (100) orientation of the second underlayer 6 is improved when the content of the substance having the BCC structure or the B2 structure in the second underlayer 6 is greater than or equal to 60 mol %.
- a magnetic storage apparatus is not limited to a particular structure, as long as the magnetic storage apparatus includes a heat-assisted magnetic recording medium according to the embodiment described above.
- the magnetic storage apparatus includes, for example, a magnetic recording medium drive unit for rotating a heat-assisted magnetic recording medium, a magnetic head provided with a near field light generation element on its tip, a magnetic head drive unit for moving the magnetic head, and a recording and reproducing signal processing system.
- the magnetic head includes, for example, a laser light generation unit for heating the heat-assisted magnetic recording medium, and a waveguide for guiding laser light generated from the laser light generation unit to the near field light generation element.
- FIG. 3 illustrates an example of a magnetic storage apparatus according to the present embodiment.
- the magnetic storage apparatus illustrated in FIG. 3 includes a heat-assisted magnetic recording medium 100 ( 100 A or 100 B), a magnetic recording medium drive unit 101 for rotating the heat-assisted magnetic recording medium 100 , a magnetic head 102 , a magnetic head drive unit 103 for moving the magnetic head 102 , and a recording and reproducing signal processing system 104 .
- FIG. 4 illustrates an example of the magnetic head 102 .
- the magnetic head 102 includes a recording head 208 and a reproducing head 211 .
- the recording head 208 includes a main magnetic pole 201 , an auxiliary magnetic pole 202 , a coil 203 for generating a magnetic field, a laser diode (LD) 204 , which serves as a laser light generation unit, and a waveguide 207 for transmitting laser light 205 generated at the LD 204 to a near field light generation element 206 .
- LD laser diode
- the reproducing head 211 includes a reproducing element 210 sandwiched by shields 209 .
- an alloy layer (underlayer) of Cr-50 at % Ti having a thickness of 50 nm was formed and heated to 250° C. Thereafter, a Cr layer (underlayer) having a thickness of 10 nm was formed. Thereafter, a Mo layer (underlayer) having a thickness of 1 nm, a MgO layer (second underlayer) having a thickness of 1 nm, and a first underlayer having a thickness of 0.3 nm were formed in this order and heated to 520° C.
- MgO-50 mol % ZnO 2 means that the content of MgO is 50 mol % and the content of ZnO 2 is 50 mol %.
- a TEM was used to measure ⁇ D> and ⁇ / ⁇ D> of MgO grains included in the first underlayer for each of Examples 1 to 6 and Comparative Examples 1 to 2.
- XRD X-ray diffraction
- Hc of the heat-assisted magnetic recording medium was measured for each of Examples 1 to 6 and Comparative Examples 1 to 2.
- Table 1 indicates the measurement results of ⁇ D> and ⁇ / ⁇ D> of the MgO grains, ⁇ 50 of the magnetic grains, and Hc of the heat-assisted magnetic recording medium for each of Examples 1 to 6 and Comparative Examples 1 to 3. Note that with respect to ⁇ 50 of the magnetic grains, as the value is lower, the orientation (001) is higher.
- an alloy layer (underlayer) of Cr-50 at % Ti having a thickness of 50 nm, an alloy layer (soft magnetic underlayer) of Co-20 at % Ta-5 at % B having a thickness of 25 nm, and a first underlayer having a thickness of 0.3 nm were formed in this order and then heated to 250° C. Thereafter, a Cr layer (second underlayer) having a thickness of 10 nm, a Mo layer (underlayer) having a thickness of 1 nm, and a MgO layer (underlayer) having a thickness of 1 nm were formed and then heated to 520° C.
- XRD X-ray diffraction
- Table 2 indicates the measurement results of ⁇ D> and ⁇ / ⁇ D> of the MgO grains, ⁇ 50 of Cr and the magnetic grains, and Hc of the heat-assisted magnetic recording medium for each of Examples 7 to 12 and Comparative Examples 4 to 6. Note that with respect to ⁇ 50 of Cr, as the value is lower, the orientation (200) is higher.
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- Magnetic Record Carriers (AREA)
- Recording Or Reproducing By Magnetic Means (AREA)
Abstract
Description
- This application is based on and claims priority to Japanese Patent Application No. 2018-121662 filed on Jun. 27, 2018, the entire contents of which are incorporated herein by reference.
- The disclosures herein generally relate to a heat-assisted magnetic recording medium and a magnetic storage apparatus.
- A heat-assisted recording method, by which a surface is locally heated by irradiating a magnetic recording medium with near-field light or the like such that writing on the magnetic recording medium is performed by reducing the magnetic coercivity of the magnetic recording medium, is known as a next-generation recording method that can realize an areal recording density of approximately 1 Tbit/inch2. Using the heat-assisted recording method, it is possible to easily write on a magnetic recording medium having a coercivity of several tens of kOe at ambient temperature by the recording magnetic field of a magnetic head. Therefore, a high Ku material whose crystal magnetic anisotropic constant Ku is on the order of 106 J/m3 can be used for a magnetic layer. As a result, while maintaining the thermal stability of the magnetic layer, the grain size of magnetic grains can be reduced to 6 nm or less. As high Ku materials, alloys such as FePt alloys (Ku≈7×106 J/m3) having an L10 structure and CoPt alloys (Ku≈5×106 J/m3) are known.
- In order to enhance the areal recording density of a heat-assisted magnetic recording medium, it is necessary to enhance the coercivity of the heat-assisted magnetic recording medium by enhancing the crystal orientation of the magnetic layer, making the magnetic grains finer, and reducing exchange coupling between the magnetic grains.
- In a case where a FePt alloy having an L10 structure is used as the magnetic layer, the magnetic layer is required to be (001) oriented in order to enhance the crystal orientation of the magnetic layer. For this reason, for an underlayer, it is preferable to use (100) oriented MgO. Here, the (100) plane of MgO lattice-matches the (001) plane of a FePt alloy having an L10 structure.
- Also, in order to make magnetic grains finer and reduce exchange coupling between the magnetic grains, it is described that an underlayer is formed that includes MgO as a main component and includes at least one kinds of oxide selected from SiO2, TiO2, Cr2O3, Al2O3, Ta2O5, ZrO2, Y2O3, CeO2, MnO, TiO, and ZnO (for example, see Patent Document 1).
- However, it is desired to further enhance the areal recording density of a heat-assisted magnetic recording medium. That is, it is desired to further enhance the coercivity of the heat-assisted magnetic recording medium.
- It is an object of one aspect of the present invention to provide a heat-assisted magnetic recording medium having excellent coercivity.
- (1) A heat-assisted magnetic recording medium includes: a substrate; an underlayer; and a magnetic layer including an alloy having an L10 structure. The substrate, the underlayer, and the magnetic layer are stacked in the recited order. The underlayer includes a first underlayer. The first underlayer includes magnesium oxide and one or more compounds selected from the group consisting of vanadium oxide, zinc oxide, tin oxide, vanadium nitride, and vanadium carbide, and a total content of the one or more compounds is in a range of 45 mol % to 70 mol %.
- (2) The heat-assisted magnetic recording medium according to (1), wherein the first underlayer is in contact with the magnetic layer.
- (3) The heat-assisted magnetic recording medium according to (1), wherein the underlayer includes a second subsurface layer, and wherein the second underlayer includes magnesium oxide and is formed between the substrate and the first underlayer.
- (4) The heat-assisted magnetic recording medium according to (1), wherein the underlayer includes a second underlayer, and wherein the second underlayer includes a substance having a BCC structure or a B2 structure, is formed between the first underlayer and the magnetic layer, and is in contact with the first underlayer.
- (5) A magnetic storage apparatus includes: the heat-assisted magnetic recording medium according to (1).
- According to one aspect of the present invention, it is possible to provide a heat-assisted magnetic recording medium having excellent coercivity.
-
FIG. 1 is a cross-sectional view illustrating an example of a layer structure of a heat-assisted magnetic recording medium according to an embodiment; -
FIG. 2 is a cross-sectional view illustrating another example of a layer structure of a heat-assisted magnetic recording medium according to the embodiment; -
FIG. 3 is a perspective view illustrating an example of a magnetic storage apparatus according to the embodiment; and -
FIG. 4 is a schematic diagram illustrating an example of a magnetic head used in the magnetic storage apparatus ofFIG. 3 . - In the following, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that in the drawings used in the following description, portions that are features may be enlarged in order to make the features easy to understand for convenience, and the dimensional ratios of respective components may not be the same as in the drawings.
- (Heat-Assisted Magnetic Recording Medium)
-
FIG. 1 is a schematic diagram illustrating an example of a layer structure of a heat-assistedmagnetic recording medium 100A according to an embodiment. - The heat-assisted
magnetic recording medium 100A includes asubstrate 1, anunderlayer 2A, and amagnetic layer 3 including an alloy having an L10 structure in this order. Here, in theunderlayer 2A, asecond underlayer 4 and afirst underlayer 5 are stacked in this order. Also, thefirst underlayer 5 includes magnesium oxide and one or more compounds selected from the group consisting of vanadium oxide, zinc oxide, tin oxide, vanadium nitride, and vanadium carbide. The total content of the above described one or more compounds is in a range of 45 mol % to mol %. Further, thesecond underlayer 4 includes magnesium oxide. - By having the above described structure, in the heat-assisted
magnetic recording medium 100A, the (001) orientation of themagnetic layer 3 including an alloy having an L10 structure is enhanced. In addition, in the heat-assistedmagnetic recording medium 100A, the magnetic grains contained in themagnetic layer 3 are made finer and exchange coupling between the magnetic grains is reduced. As a result, the coercivity of the heat-assistedmagnetic recording medium 100A is enhanced. - Here, because the
second underlayer 4 comprising magnesium oxide is (100)-oriented, thefirst underlayer 5 including magnesium oxide having a NaCl type structure is (100)-oriented. As a result, the (100) plane of thefirst underlayer 5 lattice-matches the (001) plane of themagnetic layer 3 having an L10 type crystal structure, and the (001) orientation of themagnetic layer 3 is enhanced. - Magnesium oxide grains contained in the
first underlayer 5 are made finer by the above-described one or more compounds, which are contained in thefirst underlayer 5. Then, “One by one growth” is promoted in which one magnetic crystal grain constituting themagnetic layer 3 grows on one magnesium oxide crystal grain. As a result, the (001) orientation of themagnetic layer 3 is enhanced. Also, the magnetic grains contained in themagnetic layer 3 can be made finer, separation between the magnetic grains can be prompted, and exchange coupling between the magnetic grains can be reduced. - Here, because the above-described “One by one growth” is promoted, it is preferable that the
first underlayer 5 is in contact with themagnetic layer 3, but thefirst underlayer 5 may not be in contact with themagnetic layer 3. - Note that, if vanadium, zinc, or tin in the metal state is used instead of the above-described one or more compounds, when being in contact with magnetic grains, at least portion of vanadium, zinc, or tin in the metal state diffuses into the magnetic grains and the magnetism of the magnetic grains decreases.
- The content of the above-described one or more compounds in the
first underlayer 5 is in a range of 45 mol % to 70 mol %, and is preferably in a range of 45 mol % to 55 mol %. If the content of the above-described one or more compounds in thefirst underlayer 5 is less than 45 mol %, the magnesium oxide grains in thefirst underlayer 5 cannot be sufficiently made finer. If the content of the above-described one or more compounds exceeds 70 mol %, the variance of the grain diameters of the magnesium oxide grains included in thefirst underlayer 5 increases and the (100) orientation of thefirst underlayer 5 decreases. - The content of magnesium oxide in the
first underlayer 5 is preferably greater than or equal to 30 mol %, and is more preferably greater than or equal to 45 mol %. The (100) orientation of thefirst underlayer 5 is enhanced when the content of magnesium oxide in thefirst underlayer 5 is greater than or equal to 30 mol %. - The thickness of the
first underlayer 5 is preferably in a range of 0.2 nm to 2 nm, and is more preferably in a range of 0.5 nm to 1.5 nm. When the thickness of thefirst underlayer 5 is 0.2 nm or more, magnesium oxide grains contained in thefirst underlayer 5 can be further miniaturized, and when the thickness of thefirst underlayer 5 is 2 nm or less, the heat dissipation property when writing information to the heat-assistedmagnetic recording medium 100A can be further enhanced. - The content of magnesium oxide in the
second underlayer 4 is preferably greater than or equal to 50 mol %, and is more preferably greater than or equal to 70 mol %. When the content of magnesium oxide in thesecond underlayer 4 is 50 mol % or more, the (100) orientation of thesecond underlayer 4 is enhanced. - An alloy having an L10 structure contained in the
magnetic layer 3 is preferably a FePt magnetic alloy or a CoPt magnetic alloy. - The
magnetic layer 3 preferably includes a grain boundary segregation material for magnetic grains. Thus, themagnetic layer 3 has a granular structure in which the magnetic grains having an L10 structure are divided by the grain boundary segregation material. - As the grain boundary segregation material for magnetic grains, an oxide such as silicon dioxide (SiO2), titanium dioxide (TiO2), chromium oxide (Cr2O3), aluminum oxide (Al2O3), tantalum oxide (Ta2O5), zirconium oxide (ZrO2), yttrium oxide (Y2O3), cerium oxide (CeO2), manganese oxide (MnO), titanium monoxide (TiO), or zinc oxide (ZnO), carbon (C), a carbide such as vanadium carbide (VC), a nitride such as vanadium nitride (VN), boron nitride (BN), titanium nitride (TiN), or the like may be used. Two or more of these may be used in combination as the grain boundary segregation material for magnetic grains.
- It is preferable that a protective layer is formed on the
magnetic layer 3 in the heat-assistedmagnetic recording medium 100A. - A method of forming the protective layer is not limited to a particular method. For example, a RF-CVD (Radio Frequency-Chemical Vapor Deposition) method that decomposes a source gas made of hydrocarbon by high-frequency plasma, an IBD (Ion Beam Deposition) method that ionizes a source gas by electrons emitted from a filament, a FCVA (Filtered Cathodic Vacuum Arc) method that uses a solid carbon target without using a source gas, or the like may be used to form the protective layer.
- The thickness of the protective layer is preferably 1 nm or more and 6 nm or less. The floating properties of the magnetic head become satisfactory when the thickness of the protective layer is 1 nm or more. Also, a magnetic spacing decreases and the SNR of the heat-assisted
magnetic recording medium 100A is enhanced when the thickness of the protective layer is 6 nm or less. - In the heat-assisted
magnetic recording medium 100A, a lubricant layer including a perfluoropolyether-based lubricant may be further formed on the protective layer. -
FIG. 2 illustrates another example of a layer configuration of a heat-assistedmagnetic recording medium 100B according to the present embodiment. - The heat-assisted
magnetic recording medium 100B has a configuration similar to that of the heat-assistedmagnetic recording medium 100A with the exception that anunderlayer 2B is formed instead of theunderlayer 2A. - Note that in the heat-assisted
magnetic recording medium 100B, elements that are the same as those of the heat-assistedmagnetic recording medium 100A are referred to by the same reference numerals, and duplicate descriptions may be omitted as appropriate. - The
underlayer 2B has a configuration the same as that of theunderlayer 2A with the exception that asecond underlayer 4 is not formed and asecond underlayer 6 is formed between thefirst underlayer 5 and themagnetic layer 3. - The
second underlayer 6 includes a substance having a BCC structure or a B2 structure. - Here, because the
first underlayer 5 including magnesium oxide having a NaCl type structure is (100)-oriented, thesecond underlayer 6 including the substance having the BCC structure or the B2 structure is (100)-oriented. As a result, the (100) plane of thesecond underlayer 6 lattice-matches the (001) plane of themagnetic layer 3 having an L10 structure, and the (001) orientation of themagnetic layer 3 is enhanced. - Magnesium oxide grains contained in the
first underlayer 5 are made finer by the above-described one or more compounds, which are contained in thefirst underlayer 5. Then, “One by one growth” is promoted in which one crystal grain of the substance having the BCC structure or the B2 structure constituting thesecond underlayer 6 heteroepitaxially grows on one magnesium oxide crystal grain. Also, “One by one growth” is promoted in which one magnetic crystal grain constituting themagnetic layer 3 grows on one crystal grain of the substance having the BCC structure or the B2 structure. As a result, the (001) orientation of themagnetic layer 3 is enhanced. Also, the magnetic grains contained in themagnetic layer 3 can be made finer, separation between the magnetic grains can be prompted, and exchange coupling between the magnetic grains can be reduced. - Examples of the substance having the BCC structure included in the
second underlayer 6 include Cr, a Cr—Mn alloy, a Cr—Mo alloy, a Cr—W alloy, a Cr—V alloy, a Cr—Ti alloy, a Cr—Ru alloy, and the like. - Examples of the substance having the B2 structure included in the
second underlayer 6 include a Ru—Al alloy, a Ni—Al alloy, and the like. - The content of the substance having the BCC or B2 structure in the
second underlayer 6 is preferably greater than or equal to 60 mol %, and is more preferably greater than or equal to 80 mol %. The (100) orientation of thesecond underlayer 6 is improved when the content of the substance having the BCC structure or the B2 structure in thesecond underlayer 6 is greater than or equal to 60 mol %. - (Magnetic Storage Apparatus)
- A magnetic storage apparatus according to the present embodiment is not limited to a particular structure, as long as the magnetic storage apparatus includes a heat-assisted magnetic recording medium according to the embodiment described above.
- The magnetic storage apparatus according to the present embodiment includes, for example, a magnetic recording medium drive unit for rotating a heat-assisted magnetic recording medium, a magnetic head provided with a near field light generation element on its tip, a magnetic head drive unit for moving the magnetic head, and a recording and reproducing signal processing system.
- Also, the magnetic head includes, for example, a laser light generation unit for heating the heat-assisted magnetic recording medium, and a waveguide for guiding laser light generated from the laser light generation unit to the near field light generation element.
-
FIG. 3 illustrates an example of a magnetic storage apparatus according to the present embodiment. - The magnetic storage apparatus illustrated in
FIG. 3 includes a heat-assisted magnetic recording medium 100 (100A or 100B), a magnetic recordingmedium drive unit 101 for rotating the heat-assistedmagnetic recording medium 100, amagnetic head 102, a magnetichead drive unit 103 for moving themagnetic head 102, and a recording and reproducingsignal processing system 104. -
FIG. 4 illustrates an example of themagnetic head 102. - The
magnetic head 102 includes arecording head 208 and a reproducinghead 211. - The
recording head 208 includes a mainmagnetic pole 201, an auxiliarymagnetic pole 202, acoil 203 for generating a magnetic field, a laser diode (LD) 204, which serves as a laser light generation unit, and awaveguide 207 for transmittinglaser light 205 generated at theLD 204 to a near fieldlight generation element 206. - The reproducing
head 211 includes a reproducingelement 210 sandwiched byshields 209. - In the following, Examples of the present invention will be described. Note that the present invention is not limited to Examples described below, and various variations and modifications may be made without departing from the scope of the present invention.
- On a heat-resistant glass substrate, an alloy layer (underlayer) of Cr-50 at % Ti having a thickness of 50 nm was formed and heated to 250° C. Thereafter, a Cr layer (underlayer) having a thickness of 10 nm was formed. Thereafter, a Mo layer (underlayer) having a thickness of 1 nm, a MgO layer (second underlayer) having a thickness of 1 nm, and a first underlayer having a thickness of 0.3 nm were formed in this order and heated to 520° C. Thereafter, a layer (magnetic layer) of (Fe-55 at % Pt)-40 mol % C having a thickness of 3 nm and a layer (magnetic layer) of (Fe-55 at % Pt)-40 mol % SiO2 having a thickness of 3 nm were formed in this order to obtain a heat-assisted magnetic recording medium.
- Here, the materials constituting the first underlayers are indicated in Table 1.
- For example, MgO-50 mol % ZnO2 means that the content of MgO is 50 mol % and the content of ZnO2 is 50 mol %.
- (Average Grain Diameter <D> of MgO Grains and Variance σ/<D> of Grain Diameters Normalized by Average Grain Diameter)
- A TEM was used to measure <D> and σ/<D> of MgO grains included in the first underlayer for each of Examples 1 to 6 and Comparative Examples 1 to 2.
- ((001) Orientation Δθ50 of Magnetic Grains>
- An X-ray diffraction (XRD) apparatus (manufactured by Philips) was used to measure Δθ50 of magnetic grains contained in the magnetic layer for each of Examples 1 to 6 and Comparative Examples 1 to 2.
- (Coercivity Hc of Heat-Assisted Magnetic Recording Medium)
- Using a Kerr magnetic measurement apparatus (manufactured by NEOARK CORPORATION), Hc of the heat-assisted magnetic recording medium was measured for each of Examples 1 to 6 and Comparative Examples 1 to 2.
- Table 1 indicates the measurement results of <D> and σ/<D> of the MgO grains, Δθ50 of the magnetic grains, and Hc of the heat-assisted magnetic recording medium for each of Examples 1 to 6 and Comparative Examples 1 to 3. Note that with respect to Δθ50 of the magnetic grains, as the value is lower, the orientation (001) is higher.
-
TABLE 1 MAGNETIC FIRST UNDERLAYER LAYER <D> [nm] σ/<D> Δ θ 50 OF OF MgO OF MgO MAGNETIC Hc COMPOSITION GRAINS GRAINS GRAINS [kOe] E1 MgO—50 mol 5.1 0.19 6.5 34.5 % ZnO E2 MgO—65 mol 4.8 0.21 6.7 35.8 % ZnO E3 MgO—50 mol 5.2 0.22 6.8 33.6 % V2O3 E4 MgO—50 mol 5.3 0.20 7.0 32.0 % SnO2 E5 MgO—50 mol % VN 4.6 0.21 6.9 32.7 E6 MgO—50 mol % VC 4.7 0.23 7.2 31.9 CE1 MgO—18 mol 6.2 0.19 8.1 23.4 % SiO2 CE2 MgO—75 mol 4.8 0.31 9.4 18.2 % ZnO CE3 MgO—30 mol — — — — % ZnO - From Table 1, it is apparent that, for each of Examples 1 to 6, the heat-assisted magnetic recording medium has high Hc.
- Conversely, in the heat-assisted recording medium of Comparative Example 1, because the first underlayer does not contain V2O3, ZnO, SnO2, VN, or VC, <D> of the MgO grains and θ50 of the magnetic grains are large and Hc is small.
- In the heat-assisted recording medium of Comparative Example 2, because the content of ZnO in the first underlayer is 75 mol %, σ/<D> of the MgO grains and θ50 of the magnetic grains are large and Hc is small.
- In the heat-assisted recording medium of Comparative Example 3, because the content of ZnO in the first underlayer is 30 mol %, MgO grains were not present. Therefore, measurement of θ50 and Hc of the magnetic grains was omitted.
- On a heat-resistant glass substrate, an alloy layer (underlayer) of Cr-50 at % Ti having a thickness of 50 nm, an alloy layer (soft magnetic underlayer) of Co-20 at % Ta-5 at % B having a thickness of 25 nm, and a first underlayer having a thickness of 0.3 nm were formed in this order and then heated to 250° C. Thereafter, a Cr layer (second underlayer) having a thickness of 10 nm, a Mo layer (underlayer) having a thickness of 1 nm, and a MgO layer (underlayer) having a thickness of 1 nm were formed and then heated to 520° C. Thereafter, a layer (magnetic layer) of (Fe-55 at % Pt)-40 mol % C having a thickness of 3 nm and a layer (magnetic layer) of (Fe-55 at % Pt)-40 mol % SiO2 having a thickness of 3 nm were formed in this order to obtain a heat-assisted magnetic recording medium.
- ((200) Orientation Δθ50 of Cr>
- An X-ray diffraction (XRD) apparatus (manufactured by Philips) was used to measure Δθ50 of Cr included in the second underlayer for each of Examples 7 to 12 and Comparative Examples 4 to 5.
- Table 2 indicates the measurement results of <D> and σ/<D> of the MgO grains, Δθ50 of Cr and the magnetic grains, and Hc of the heat-assisted magnetic recording medium for each of Examples 7 to 12 and Comparative Examples 4 to 6. Note that with respect to Δθ50 of Cr, as the value is lower, the orientation (200) is higher.
-
TABLE 2 MAG- NETIC SECOND LAYER FIRST UNDERLAYER UNDER- Δ θ 50 OF <D> [nm] σ/<D> LAYER MAG- COMPO- OF MgO OF MgO Δ θ 50 NETIC Hc SITION GRAINS GRAINS OF Cr GRAINS [kOe] E7 MgO—50 5.1 0.19 4.6 6.7 30.5 mol % ZnO E8 MgO—65 4.8 0.21 4.7 6.9 31.6 mol % ZnO E9 MgO—50 5.2 0.22 6.8 6.9 29.8 mol % V2O3 E10 MgO—50 5.3 0.20 6.1 7.1 28.3 mol % SnO2 E11 MgO—50 4.6 0.21 7.5 7.1 29.0 mol % VN E12 MgO—50 4.7 0.23 5.8 7.4 28.2 mol % VC CE4 MgO—18 6.2 0.19 8.1 9.6 16.6 mol % SiO2 CE5 MgO—75 4.8 0.31 9.4 10.1 15.1 mol % ZnO CE6 MgO—30 — — — — — mol % ZnO - From Table 2, it is apparent that, for each of Examples 7 to 12, the heat-assisted magnetic recording medium has high Hc.
- Conversely, in the heat-assisted recording medium of Comparative Example 4, because the first underlayer does not contain V2O3, ZnO, SnO2, VN, or VC, <D> of the MgO grains and θ50 of Cr and the magnetic grains are large and Hc is small.
- In the heat-assisted recording medium of Comparative Example 5, because the content of ZnO in the first underlayer is 75 mol %, σ/<D> of the MgO grains and θ50 of Cr and the magnetic grains are large and Hc is small.
- In the heat-assisted recording medium of Comparative Example 6, because the content of ZnO in the first underlayer is 30 mol %, MgO grains were not present. Therefore, measurement of θ50 and Hc of Cr and the magnetic grains was omitted.
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